A mid‑August cumulative update for Windows 11 — KB5063878 (OS Build 26100.4946), released on August 12, 2025 — is being linked by multiple independent community tests and tech outlets to a storage regression that can render some SSDs inaccessible after sustained, large sequential writes, with affected drives reportedly disappearing from the OS and, in some cases, exposing file corruption and unreadable SMART data. Background / Overview
Microsoft released KB5063878 on August 12, 2025 as the...